Telephone system



Sept 19, 1933- G. E. STONEBRIDGE, JR 1,927,531

TELEPHONE S YS TEM Filed March l1, 1932 Patented Sept. 19, 1933 UNITED .STATES TELEPHONE I SYSTEM George E. Stonebridge, Jr., New York, N. Y., assignor to Associated Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Application' March 11, 1932. `'Serial No. 598,135

14 Claims.

This invention relates to telephone systems in general and is concerned particularly with 'small systems for private installation; The object of the invention is the provision of a simple and inexpensive system for supplying the type of telephone service suitable for schools and other similar establishments.

In the system comprising the invention a number of stations hereinafter referred to as extension stations are permitted to call a central or supervisors station only, while the supervisors stationis permitted ,to call any of the extension stations. Calls from extension stations are made by merely lifting the receiver from the kswitch-- hook, whereupon the supervisors station is sig-- nalled automatically. The supervisors station is provided with control equipment for seleetively signalling the extensiony stations. All vconnections are guarded against intrusion, and any station attempting to callwhile another call is in processis given a busy signal.

The various features of the invention will be discussed in connection with` the detailed description of the system disclosed in the accompanying drawing. The system shown is designed for a maximum of twenty-ve extension stations and one supervisors station. The capacity of the system in regards extension stations is dependent upon the size of the iinder-connector switch provided and accordingly the number of stations served can be vincreased by providing a switch of suitable capacity. Referring now to the drawing, two extension `stations L-l and 11-25 and their respective lines andindividual line relays are shown at the left side of the drawing. The telephone sets provided for these stations are of the type commonly used in manualtelephone systems. The individual line relays are of the so-called twostep type which operate certain-armatures Vdesignated by the roman numeral I when energized over one winding and which actuate these armatures and also those designated bythe roman numeral II when energized over the other wind-- The finder-connector- `switch `FC is a rotary Switch of the type whose wipers have no normal or home position and which move only in a forward direction'. The wipers engage bank contacts which are assigned k.to the various extension lines.` A group of relays associated with this switch controls the signalling otra called station, battery-feed'and the release of connections.

The busy tone and ringing current generator and interrupter, which is shown diagrammatically, may be of the relay type, such as that disclosed inLomaX Patent No. 1,750,934 of March 18,1930, simplified by the omission of the dial tone relays and all but one of the ringingcurrent leads. To better illustrate the interconnection of' this equipment with the switching apparatus, thereference characters used in the above patent have been applied to corresponding conductors of the instant disclosure. (i5

The supervisors station" is, connected directly with the relay equipment and is assigned no Vcontacts ,in the banks of the finder-connector switch..v The supervisors station incidentally `ifs provided with an ordinary manual type telephone set modied by the addition of a set of contacts controlled by the switchhook which serves to connect up the calling device or Vdial D when used.

The marking switch M shown in the lower portion of the drawing is generally similar to the ordinary Strowger type selector switch and is controlled from the supervisors station bythe calling device D.' The switch has accessto contacts connectedindividually with the various extension line relays and serves to mark a particular line as the called line and to initiate the operationrof nder-connector FC in calls originating at .the supervisors station. An alternative arrangement for lcalling has beenV shown employing keys individual to the extension lines instead of the common switch M. When this alternative-arrangement is'used, .the conductors shown connected to the bank of the switch M are connected instead to the Vconductors which extend to the supervisors station and terminate there- ,at in keys K and Kl.' With this arrangement a dial at the Vsupervisors vstation will not be required and, accordingly, may be omitted.

The operations involved in `establishing various connections in the system will now be described -in detail. vAssumingthat the subscriber at station L1 initiates a call by lifting `his receiver, re-

lay Seperates over avcircuit which may be traced from battery throughvthe lower winding of the relay, contacts 4, line conductor 2 through the 100 loop at the calling station, line conductor 1, contacts 9, conductor 15, and contacts 28 to ground. As previously stated, relay 3 when energizedover its lower winding actuates only the armatures designated by the v-roman numeral 1, thereby at contacts l0 connecting its upper winding to conductor 11 which terminates in a contact accessible to wiper 16 of the finder switch FC. At

contacts V'Z ground is removed from conductor 12A whichV terminates in acontact accessible to wiper 119 17 of the finder-connector and at contacts 6 ground is applied to conductor 13 to operate relay 18. Relay 18 completes the generator and tone starting circuit by connecting ground to starting conductor 24 at contacts 76, and at contacts 20 connects motor magnet MM to wiper 17. In case the switch wipers at this time are standing on contacts other than those of the calling line, wiper 17 will nd ground by way of a conductor, such as conductor 12, and the contacts of the line relay and the motor magnet operates. The motor magnet opens its own circuit at contacts 19 and, on deenergizing, advances the Wipers to the next set of contacts. This operation is repeated as longas wiper 17 engages grounded contacts. When the contact associated with the calling line is encountered, Wiper 17 will find no ground due to the opening of contacts 7andthemotormagnet is not energized. Relay 3 now operates in its second step from ground at contacts 25, wiper 16 and the engaged bank contact, conductor 11, contacts 10, upper winding of the relay to battery. The line conductors are thereby disconnected from the circuit including the lower winding of relay 3 by the opening of contacts 4 and 9, and at contacts 5 and 8 are extended over conductors and 14, contacts 30 and 35, through the upper and lower windings of relay 3 to battery and ground, respectively. Relay 23 operates and closes the ringback-tone circuit at contacts 37; disconnects relay 22 from the supervisors line at contacts 38 and 43; completes the ringing circuit at contacts 39 and 42; closes a circuit for relay 21 at contacts 40, and prepares a holding circuit for the connection of contacts 41.v Relay 21 operates after a slight delay, opens the orginal circuit for the upper winding of relay 3 at contacts 25 and completes a new circuit for therelay by way of contacts 26 and 41. The original energizing circuit of the line relay and other line relays is opened at contacts 28 and at contacts 27 the remaining lines are connected Via a condenser and conductor 174 to the busy tone generator. Ringing current and ground are now applied'al- Aternately to the supervisors line over a circuit extending from the ringing generator and interrupter, conductor 173, contacts 49 and 42, line conductor 81 through the condenser and bells at the supervisors station, l'rne conductor 82, contacts 39 and 45, upper winding of relay 83 to battery. The bell at the supervisors station rings intermittently. Relay 83 doesv not operate at this time due to the inclusion of the condenser in the circuit. When the call is answered a direct current bridge is completed across the line conductors at the supervisors station, and relay 83 operates over the previouslytraced circuit, opens the ringing circuit at contacts 45 and 49; completes the talking circuit at contacts 46 and 48, and completes a locking circuit for its lower vwinding at contacts 47. The calling and called stations are now directly connected over` the'conductors indicated by the heavy lines kand talking current is fed to both stations through the windings of relay 23.

' In case another station attempts to call at this time the associated line relay does not operate upon the initiation of the call due to the disconnection of ground from the starting circuit at contacts 28. The calling-subscriber will be given a busy tone, however, by way of contacts 27 and conductor 174.

At the termination of the call, both subscribers will restore their receivers tor the switchhook,

thereby opening the station loop circuits and relay 23 restores. Relay 23 opens the talking circuit previously described, opens the circuit of relay 21 at contacts 40 and opens the holding circuit for the line relay and for relay 83 at contacts 41. Relay 21 is slow-to-release as well as slow-to-operate and maintains its armatures actuated for a short interval after its circuit is opened as described. Accordingly, upon the release of relay 23, line relay 3 of the calling line releases immediately; opens its own holding circuit at contacts 10, and restores the line conductors to their normal connection with the lower winding of the relay. When relay 21 nally restores, ground is again applied to wiper 16 by way of contacts 25 and the busy tone is disconnected from the starting circuit at contacts 27 and the starting circuit is again rendered effective by the closure of contacts 28. The wipers of the finder connector are not moved from the contact last used until new call is initiated.

A call from the supervisors station to exten'- sion station L-25 will now be described. The

lifting of the receiver completes a loop circuit over line conductors 81 and'82, contacts 38 and 43 for the upper and lower windings of relay 22 which operates. Relay 22 prepares the talking circuit by closing contacts 29-and 36; disconnects line relay 23 from the talking conductors at contacts 30 and 35; prepares the ringingcircuit at contacts 31 and 34; completes a circuit for relay 21 at contacts 32, and prepares a circuit for operating the line relay of the called line at contacts 33. from wiper 16 at contacts 25 and immediately connects another ground to that wiper by way of contacts 26 and 33. A further result of the lifting of the receiver is the closure of the circuit from ground, contacts 50, impulse contacts 51 of the dial, conductor 52, relay 53 to battery which operates relay 53. Relay 53 at contacts 54 completes a circuit for relay 54 and in parallel therewith by Way of contacts 69 for the upper winding of relay 55. Relays 54 and 55 operate and at contacts 59 and 61, respectively, prepare a circuit for the vertical magnet VM. The calling party now dials the number assigned to the wanted extension line, the rst digit of which, for example, may be the digit 2. The circuit of relay 53 is opened twice at the impulse contacts of the dial and on each restoration of relay 53 a circuit is completed by way of contacts 75, 59, and 61 for the vertical magnet. The magnet operates and raises the switch wiper to the second level of contacts accessiblein its bank. It will be noted that the lower winding of relay 55 is connected in parallel with the magnet which serves to maintain the relay operated throughout the series of impulses after its initial energizing circuit is opened at vertical off-normal contacts 69 when the wipers leave normal position. Shortly after the last impulse relay 55 restores and transfers the impulsing circuit by way of contacts 62 and Relay 21 operates, removes ground tacts 63 for'the lowerwinding of relay'?, and at contacts 65 short-circuits contacts 68 to maintainl the impulsing circuit closed upon the opera'- tion of relay 57. Relay 57`cor 1pletes` a locking *Y ,circuit for its upper winding by way ofY contacts v lby the calling party will be inefiectivehenceforth,

due to the openingof the impulse circuit at con- Ytacts and 68. Referring now to the called line equipment, relay-3 operates in its rst step' in thesame manner as when a call is initiated by the subscriber at station L-25. A circuit for the upper winding fof the yrelay isiprepared at contacts 10', `a circuit for relay 18 is completedV at contacts 6', and 'the line is marked in the bank of the finder switch by the opening ofV contacts '7'. Relay 18 operates vand initiates the operation of the rotaryY magnet las for the preceding call.` When the` called line is found' by the finder-connector, relay 3 operates over its upper winding and wiper 16 thereby extending the line conductors 1 and 2 by way of contacts 5 and 8', conductors 80 and 14, contacts 31 and 34contacts 45 and 49,r through the upper winding ofV ring-cut-o relay 83 and to ground or generator, respectively. The bellat the lcalled station rings intermittently and, when the (call is answered, a direct current bridge is closed across .the line conductors at the called station. Relay 83 operates, opens the ringing circuit and fl-l-- 'completes the talking circuit. The called station and the supervisors station are now directly connected as in the previous case except that the talkingcircuit now includes contacts 29, 31, 32, and 36 and battery and ground for talking purposes are fed through relay 22. The release of 1356 32, thereby permitting the various relays to restore as inthe previous connection.

In using the.. alternate calling arrangement shown,'the switch M and the dial at the supervisors station are omittedand the conductor is extended from the line relay of each extension line to a key at the supervisors station. In calling the-station L-25, for example, the procedure is exactly the same as that above described, except that instead of dialling, the supervisor will operate key K, thereby applying ground by way of contacts 85, conductor 77 and conductor 72 to the lower winding of relay 3'. The remaining operations are exactly the same as those previously described.

What is claimed is:

1. In a telephone system, two lines, a link for connecting said lines, two battery feed bridgesin the link for supplying talking current to said lines after they are connected, and means dec pendent on which of said lines is the calling line for determining which one of said bridges shall be eiective during the call.`

2. In a telephone system, a link adapted to be seized at either end to extend a call, two battery feed bridges for the link, means controlled bythe seizureofthe'link at one end for rendering one of said bridges-eiiective to feed battery to both the calling and called party, and means controlled by the seizure of theV link at the other end for rendering the other of'said bridges effective to 'feed battery to both the calling and called party'. 3. In a telephone system, two lines, a linkfor connecting the lines, two line relays for the link, `means responsive-to a call originating on one line 'for operating one-,of said relays and for disconnecting the other of lsaid relays, and means responsive to a call originating on theother of said lines for operating said other' relayand for disconnecting said one "relay, i

4. In Va telephonev system, two lines, a link for connecting said lines, a relay in the linkoper'- ated responsive to a call originating onV one line, a second relay in rthe link' operated responsive to a callf'originating on the other line, a source of signalling current, and means controlled by either relay for connecting saidsource to the non-calling line. v

Y 5. In a telephone system, a link adapted to be seized at either end to extend al call, a relay in the link operated 4responsive to the seizure of the link at one end, a second relay in the link operated responsive to the seizure of the link at the other enda source of signalling current, and means controlled by said relays for connecting said current source to the Vlink at the end opposite .the seized end.

' 6. In a telephonesystem, a pluralityV of subscribers lines, a supervisors line, a common connecting link, means responsive to the initiation of'a call on any subscribers line for connecting the line to the link and for intermittently applying ringing current to the supervisors line, and means lcontrolled over the supervisors line for vstopping the application of ringing -current thereto'and for connecting the Asupervisorsrline directly with the calling`line. f7. In a telephone system, a plurality of subscribers lines, a supervisors line, a link circuit terminating the supervisors line, a finder switch associated with said link and having access to said subscribers lines, means responsive to the initiation of a call on the subscribers line for operating said switch to connect the calling line to said link and to apply signalling current to the supervisors line, means responsive to the initiation of a call in the supervisors line for preparing the link circuit for applying signalling current to a subscribers line, and means controlled by the supervisor for operating said finder to connect a particular subscribers line with the link circuit whereby that line is signalled by current applied from the link.

8. In a telephone system, a plurality of subscribers lines, a supervisors line, a link circuit for connecting any subscribers line with the supervisors line, a relay for each subscribers line, a circuit for each relay including the associated line and a common source of potential, means responsive to the initiation of va call on a vsubscribers line for operating the associated line nating the supervisors line, a finder switch associated with said link and having access to said subscribers lines, means responsive to the initiation of a call on a subscribers line for operating said switch to connect the calling line to said link and to apply signalling current to the supervisors line, means responsive to the initiation of a call on the supervisors line for preparing the link circuit to apply signalling current to a subscribers line, and a switching device directively controlled by the supervisor for selecting a subscribers line for connection via said nder switch to the link to receive the signalling current from said link.

10. In a telephone system, a plurality of lines, another line, a iinder switch associated with said other line, wipers for the switch, contacts indi- Vidual to said first lines accessible to the switch via said wipers, means responsive to the initiation of a call on one of said rst lines for operating said switch to set its wipers on the contacts associated with the calling line, and means responsive to the wipers engaging said contacts vfor connecting the calling line with said other line independent of said wipers.

11. In a telephone system, a plurality of lines, another line, a nder switch associated with said other line, wipers for the switch, contacts individual to said rst lines accessible to the switch via said wipers, means responsive to the initiation of a call on one of said rst lines for operating said switch to set its wipers on the contacts associated with the calling line, means responsive to the wipers engaging said contacts for transmitting a call signal over said other line,A and means responsive .to the answering of the call for directly connecting the calling line and said other line independent of the wipers of said switch.

12. A telephone system for schools, or similar establishments, said system comprising a super- Visors station at the oince of Ythe supervisor, a number of extension stations located at the various class rooms, a link circuit having one end extending to the supervisors station, switching apparatus at the other end of said link for connecting the same to any extension station, means responsive to the removal of the receiver at any extension station for operating said switching apparatus to connect such extension station to said link, means responsive to such connection for signalling the supervisors station, and means also responsive to such connection for barring other extension stations from obtaining connection with said link.

13. Atelephone system as set forth in claim 12, in which a call from the supervisors station to an extension station may be initiated by the supervisor, said system including means independent of the link for signalling any desired extension station, thereby notifying the party at such extension station to remove the receiver and obtain connection with the link to answer the call.

14. A system for supplying telephone service to the supervisors oce and the various class rooms of a school, the requirements of the service contemplating calls from any room to the oce and from the oiiice to any room but prohibiting calls from one room to another, said system comprising a supervisors station and a number of extension stations located in the various rooms, a link circut having one end extending to the supervisors station, means at the other end for connecting said link to any extension station, means separate from the link for signalling any extension station from the supervisors station, means responsive to the removal of the receiver at an extension station to answer a call from the supervisors station or to initiate a call to the supervisors station for operating the said connecting means, thereby connecting such extension station over the link to the supervisors station, and means effective only if the call is initiated at an extension station for signalling the supervisors station.

GEORGE E. STONEBRIDGE, JR. 

